1. Field of the Invention
This invention relates to an ophthalmic measuring apparatus used, for example, in ophthalmic hospitals or the like and having the function of measuring the distance between pupils, the function of measuring the inter-lens distance of lenses to be examined, and further the function of measuring the refractive values of the lenses to be examined.
2. Related Background Art
When prescribing spectacle lenses for a patient, it is of course important to measure the eye refractive values of eyes to be examined by an autorefractometer, to measure the vertex refractive values of spectacle lenses and inspect the fit of the spectacle lenses, as well as to inspect whether the difference between the distance between the pupils of the eyes to be examined and the inter-lens distance of the spectacle lenses is within an allowable range. This is because when this difference is great, a light beam entering the eye to be examined is not transmitted through the center of the spectacle lens and therefore deviation of the image and distortion and astigmatism by a prism action occur, thus causing two images to be seen and causing a reduction in sight and distortion. Moreover, in the case of spectacle lenses which are great in refractive power, even a slight difference greatly affects the patient.
So, in the past, the measurement of the inter-lens distance has been effected by the use of a method of measuring the distance between pupils by an inter-pupil distance meter utilizing reflected light beams from corneas, or a scale incorporated in an auto refractometer, and on the other hand, by printing marks at the centers of spectacle lenses in conjunction with a point printing function incorporated in a lens meter, and measuring the distance between the marks with a scale.
However, in such a system, the measurement of the refractive values of the eyes, the measurement of the refractive values of the spectacle lenses, the measurement of the inter-pupil distance, and the measurement of the inter-lens distance are effected by discrete apparatuses, and this is not preferable from the viewpoints of measurement efficiency and apparatus installation space, and is also subject to the risk of making a mistake in combining the measurement data. Also, as previously described, the allowable range of the difference between the inter-pupil distance and the inter-lens distance differs, depending on the refractive power of spectacle lenses and therefore, an overall judgment of the measurement data becomes necessary. But such a prior-art system suffers from the problem that this overall judgment is difficult to perform.